Posted on 04/12/2011 1:32:09 PM PDT by grundle
Texas Instruments TI-85 says:
48÷2(9+3) = 2
But Texas Instruments TI-86 says:
48÷2(9+3) = 288
to a Vinculum (_____)
and the correct answer becomes obvious
48
2(9 + 3)
It's so much easier to multiply fractions than add them when teaching kids they have to have a common denominator.
They really whine when they find out they're not done and they need to reduce!
Hubby says you’re right. :D
Both are correct!
It depends on the convention.
If division has lower precedence than multiplication, then the multiplication is done first, 2*12=24, then the division 48/24 = 2.
If division and multiplication have equal precedence, then the division is done first, 48/2 = 24, then the multiplication, 24*12=288.
So both could be correct depending on how the operator precedence is treated.
“48/2(9+3) = 48/2*(9+3)
It is the same”
Therein lies the source of this threads misunderstanding.
The two terms are not equal. But (incorrectly) rewritting the first term into the second is the only way you can get to 288.
For those of you who claim you can multiply and divide in any order, consider that if you multiply 2 and 12 first, you get 24. If you then divide 48 by 24, you get 2.
Therefore, using your own logic, an answer of 2 is just as correct as 288.
After all isn’t ab = ba?
All you 288ers are simply wrong.
Please cite a source for this "convention."
I have already provided a link to the google page for the order of operations. That's what the 288 people are following.
Where are your rules documented?
Shall I make a copy of the chapter of our 4th grade math book that teaches 2(9+3) is the same as 2x(9+3)? That is absolutely what it teaches.
Nobody says that. Many, many people have posted the order of operations. Multiplication and division have equal precedence and are evaluated left-to-right.
Those are the rules.
Follow them and see what answer you get.
Thank you!
That is to say, when you type “48/2(9+3)” on the calculator, you are talking to a computer not a human. You have to conform to its rules of operator precedence.
If 2(9 + 3) is not the same as 2 * (9 + 3), then what is the difference? Please cite a source.
I get “9 plus 3 equals 12 times 2 equals 24” for both.
What is this magical new arithmetic operation, if it is not multiplication?
And my source is impeccable:
Sister Mary from the 4th grade and she got her info straight from God.
Do your 4th graders know how lucky they are to have you as a teacher?
Tell them to learn it all as it comes up now & they won’t have to take remedial math classes in college where they will be expected to learn 9 months of math in one 14 - 16 week semester.
I went back to the ancient algebra book; and, it didn't say a peep about this. All of the examples show a left-to-right parse given equal precedence. The rules regarding commutivity and associativity really do point to the answer being 288.
Anyone who knows the word Vinculum must be correct.
That's the way my mind sees it. That's the way we used to write it. I wish the computer allowed me to easily type it!
I’ll tell them but I’m sure they won’t believe me :)
Are all of the rules of order posted on the internet wrong? Should they be:
Parentheses (inside)
Parentheses (any multiplication outside the parens, as long as they didn’t explicitly use a multiplication symbol)
Exponents
Mult and divide
Add and sub
Looks like you’re the only one left who doesn’t get it (or won’t admit it). Or, you’re messing with us.
The reason we have precedence rules is to avoid misunderstanding how operators should be applied. You can say “48 divided by 2 x (9+3) is not the same as 48 divided by 2(9+3)” but you’d be wrong. Using the language of math, we start with an ordered set of rules and an equation.
Rules:
Ops inside parens are evaluated first
Mult & Div operations are equal and are applied next
Add & Subt ops are equal and are applied last
If 2 operations have the same precedence, apply them from left to right.
The equation:
48/2(9+3) (which is the same as saying 48/2*(9+3). The * is implied in the first form.)
According to the rules, we evaluate the operations *inside* the parens first and get
48/2(9+3) =
48/2(12) =
48/2*12
Now that the parens have been evaluated, apply the mult and div operations. This problem has 2 of them, so evaluate from left to right:
48/2*12 =
24*12 = 288
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